$K_{a_1}, K_{a_2}$ and $K_{a_3}$ are the respective ionization constants for the following reactions $(a), (b),$ and $(c)$.
$(a)$ $H_2C_2O_4 \rightleftharpoons H^{+} + HC_2O_4^-$
$(b)$ $HC_2O_4^- \rightleftharpoons H^{+} + C_2O_4^{2-}$
$(c)$ $H_2C_2O_4 \rightleftharpoons 2H^{+} + C_2O_4^{2-}$
The relationship between $K_{a_1}, K_{a_2}$ and $K_{a_3}$ is given as

• A
  $K_{a_3} = K_{a_1} + K_{a_2}$
• B
  $K_{a_3} = K_{a_1} - K_{a_2}$
• C
  $K_{a_1} = K_{a_3} / K_{a_2}$
• D
  $K_{a_3} = K_{a_1} \times K_{a_2}$